This application relates to a refrigerant compressor wherein a vapor/liquid mixture is injected into intermediate pressure chambers through the economizer ports, thus removing any necessity for providing separate ports for vapor injection and for liquid injection.
Compressors are utilized to compress refrigerant for refrigerant compression applications such as air conditioning, refrigeration, etc. There are many challenges to the provision of the most efficient control of refrigerant circuits. In particular, under certain operational conditions, it would be desirable to achieve increased capacity or increased efficiency operation for the refrigerant circuit. One way of achieving increased capacity or increased efficiency is the inclusion of an economizer circuit into the refrigerant circuit. An economizer circuit essentially provides heat transfer between a main refrigerant flow downstream of a condenser and a second refrigerant flow which is tapped downstream of the condenser and passed through an expansion valve. The main flow is cooled in a heat exchanger by the second flow.
In this way, the main flow from the condenser is cooled before passing through its own expansion valve and entering the evaporator. Since the main flow enters the expansion valve at a cooler temperature, it has greater capacity to absorb heat in the evaporator which results in increased system cooling capacity. The refrigerant in the second flow enters the compression chamber in the compressor at a point downstream of suction and upstream of discharge. That is, the refrigerant from the second flow line is injected into economizer ports at an intermediate compression point. Because the injector vapor is at an intermediate pressure, it requires less energy to compress it to the discharge or condenser pressure than if it has been injected at the suction or evaporator pressure. This results in a reduction of specific work in the compressor which in turn results in improved system efficiency.
One type of compressor which utilizes an economizer is a scroll compressor. Typically, a pair of spaced economizer injection ports inject the fluid into the intermediate pressure chambers.
Recently, a system has been developed by the assignee of this application wherein an unloader valve function also operates through the economizer ports. A valve is selectively opened to control the unloader function, and allow fluid to flow from the economizer ports through the unloader valve and back to a suction supply line.
Further, it is sometimes desirable to provide a liquid/vapor refrigerant mixture into the compression chambers to reduce the discharge temperature of the refrigerant. At certain operational conditions, lowering the discharge temperature has significant benefits. In particular, at high saturated condensing temperature, high pressure ratio, or high superheat conditions, it is desirable to lower the discharge temperature. Injecting a vapor/liquid mixture into the compression chambers has the effect of lowering the discharge temperature. However, in general separate injection ports have been utilized. It is also common for a single set of ports to be provided for either economized operation or for liquid injection, but not for both.
In the disclosed embodiment of this invention, an economizer return line selectively communicates with a liquid tap tapping liquid refrigerant downstream of the condenser. A valve on this liquid tap line selectively communicates the liquid to the economizer return line, and eventually through the economizer ports into the compression chambers. This valve can be open when it is desired to lower the discharge temperature of the refrigerant. The valve can be opened in combination with the economizer valve being open, or could be used when the economizer valve is closed. Further, the valve may be utilized to supply the liquid during unloaded operation.
By injecting the liquid through the economizer ports, the provision of separate economizer and liquid injection ports is made unnecessary. Further, the injection of the liquid refrigerant into the intermediate location, rather than the prior art injection at suction does not dilute the compressor sump.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.